A calorimetric study of carbamate formation

Investigations of primary and secondary amine carbamate stability by 1H NMR spectroscopy for post combustion capture of carbon dioxide

“…Our values for DH o m and DS o m are À18(1) kJ Á mol À1 and À25(3) J Á K À1 Á mol À1 , respectively. The former is intermediate within the reported data range for DH o m , but lower than the calorimetrically-determined value, while DS o m is also lower than the reported value [20]. Smaller variations in log 10 K 9 and DH o m appear for DEA.…”

“…However, there is a considerable spread in the reported value for DH o m . Values vary from À13(2) to À33(2) kJ Á mol À1 [13,[15][16][17], and a value for DH o m based on isothermal titration calorimetry of À29.7(1) kJ Á mol À1 , with an accompanying value for DS o m of À69.0(7) J Á K À1 Á mol À1 , has been recently reported [20]. Our values for DH o m and DS o m are À18(1) kJ Á mol À1 and À25(3) J Á K À1 Á mol À1 , respectively.…”

“…Our log 10 K 9 value is in good agreement with the reported data (table S1), but again there is considerable variation in DH o m . Values range from À12.4 to À34.1 kJ Á mol À1 [14,17,21], with a calorimetricallydetermined value for DH o m of À23.7(9) kJ Á mol À1 , and a DS o m of À63(4) J Á K À1 Á mol À1 [20]. Our values of À18(1) kJ Á mol À1 and À44(4) J Á K À1 Á mol À1 for DH o m and DS o m , respectively, are slightly lower than those reported in the recent calorimetric study.…”

“…The pathway (K 9 ) given by equation (3) is much easier to study experimentally, as opposed to K 10 , and hence it is easier to evaluate an equilibrium constant for this reaction (note that equation (3), K 9 , has been the dominant reaction pathway used in the literature for which carbamate stability constants have been reported, and is often designated as K carb [8][9][10][11][12][13][14][15][16][17][18][19][20][21]). By microscopic reversibility, it is possible to calculate values for K 10 , equation (11), by the expression K 10 = K 9 Á K CO2 , with equilibrium data for K CO2 obtained from reference [26].…”

“…Few data are available for comparison, and of the present library of amines, only values for MEA and AP have been reported. The log 10 K 8 for MEA has been reported as 7.49(2) at T = 303 K [19] and 7.93(7) at T = 298 K [20], while that of AP is 8.0(2) at T = 303 K [19]. For MEA, there is also a value for log 10 K 8 of 6.5 at T = 298 K based on kinetic studies [23].…”